Explanation:
Why are parts of this asteroid's surface so smooth?
No one is yet sure, but it may have to do with the dynamics of an
asteroid that is a loose
pile of rubble rather than a solid rock.
The unusual asteroid
has been visited recently by the
Japanese spacecraft
Hayabusa
that has been documenting its unusual structure and mysterious
lack of craters.
Recent analyses of the border regions
between smooth and rugged sections of Itokawa indicate that jostling of the asteroid might be creating segregation between large and small rocks near the surface, like the
Brazil nut effect.
In late 2005, Hayabusa actually touched down on one of the smooth patches, dubbed the MUSES Sea, and
collected soil samples that are to be returned to Earth for analysis.
Hayabusa will start its three-year long
return trip
to Earth this month.
Computer simulations show that 500-meter asteroid Itokawa
may impact the Earth within the next few million years.